Biological factors involving Trypanosoma cruzi life cycle in the invertebrate vector, Rhodnius prolixus.

Trypanosoma cruzi, the ethiologic agent of Chagas disease (Chagas 1909), is transmitted through triatomine vectors during the meal on the invertebrate host. The parasite displays quite distinct morphological and functional forms, alternating between replicative stages (epimastigotes in the vector midgut and amastigotes in vertebrate cells) and infective, non-dividing forms (metacyclic trypomastigotes in the vector, which are deposited together with feces and urine, and bloodstream trypomastigotes in mammals) (for revision see Brener 1973, Zeledon 1974, Garcia & Azambuja 1991, 1996, Gonzalez et al. 1998a). Because of the importance of Chagas disease in Latin America a great effort has been devoted to develop an experimental model that could imitate basic features on T. cruzi life cycle in the invertebrate vector. Thus, we developed in our laboratory the Rhodnius prolixus model to study several parameters related to the high degree of interaction between T. cruzi and invertebrate vector. Basically, this model implies in feeding of larvae and adults of R. prolixus, through a special membrane feeding apparatus, on blood containing different strains/clones of T. cruzi and, at different intervals, determination of the number of parasite in the gut, urine and feces of the vector (see Garcia & Azambuja 1991, 1996, Gonzalez et al. 1998a, 1999). Herein, we will describe experiments, using this useful parasite-vector model, to elucidate some mechanisms involved in the interaction T. cruzi-triatomine insect and also link insect factors with the success or the failure of strains/clones of parasites to establish the infection in the digestive tract of the vector.